Process of preparing quinoline



3,020,282 Patented Feb. 6, 1962 3,020,282 PROCESS F PREPARENG QUTNQLINEFrancis E. Cislak and William R. Wheeler, Endianapolis,

Ind, assignors to Reilly Tar & Chemical Corporation,

Indianapoiis, Ind a corporation of Endiana No Drawing. Filed .i'uly 22,1957, Ser. No. 673,150

3 Claims. (Cl. 260- 283) This invention relates to a process ofpreparing quinoline. More specifically, it relates to a process ofpreparing quinoline by the interaction of acetaldehyde, formaldehyde,and aniline.

.The quinoline of commerce is isolated from coal tar distillates. Theamount that can be produced in this manner is limited. A classicalmethod of synthesizing quinoline is the Skraup synthesis. The Skraupprocedure involves an interaction of aniline with glycerine, sulfuricacid, and an oxidizing agent. The main drawback to the Skraup method isthat it does not readily lend itself to continuous operation.

We have found that we can prepare quinoline in a continuous manner bythe interaction of acetylene or acetaldehyde with formaldehyde andaniline.

In carrying out our invention, we prepare a mixture of acetaldehyde andformaldehyde. This acetaldehydeformaldehyde solution is then vaporized,mixed with yaporized aniline, and the resultant mixture is passedthrough a suitable reactor containing a catalyst. The temperature of thereactor is maintained between about 400 C. and 550 C. and preferablybetween about 450 C. and 500 C. We prefer to conduct our process in a.continuous manner although that is not necessary.

The reactor used may be of various types. We prefer the fluid catalysttype, similar to those normally used in carrying out cracking operationsin the petroleum industry. Such reactors are of tubular form withsuitable connections at entrance and exit. They are provided with meansfor supporting the fluid bed of catalyst, and are provided with anyconvenient means for heating them.

The catalyst used may be any of a large number of catalysts which areuseful in the preparation of 2-picoline and 4-picoline from acetyleneand ammonia.

Illustrative of the manner in which our invention may be carried out, Wecite the following example. The parts are by weight.

Example] To 41 parts of acetaldehyde we add 110 parts of an aqueousformaldehyde solution containing 25% f0rma1- dehyde. The resultingacetaldehyde-formaldehyde solution is vaporized, mixed with anilinevapors to prepare a gaseous mixture composed of about equal parts ofacetaldehyde-formaldehyde solution and of aniline. We pass the mixtureof vapors through a fluid catalyst type reactor containing a fluidizedcatalytic bed of silicaalumina catalyst (13% alumina). The temperatureof the reactor is maintained at about 450 C. As the vapors of aniline,acetaldehyde, and formaldehyde pass through the reactor, 2. reactionoccurs whereby quinoline is formed. The vapors of the unchangedreactants and the reaction products are condensed as they emerge fromthe reactor, and the condensate is collected in a suitable receiver. Thecondensate as recovered contains more than 50% water. This water may beremoved by the addition of flake caustic soda. The resulting dry crudebases are fractionally distilled through an efficient fractionationcolumn. Instead of acetaldehyde, we may use aletylene. If we useacetylene in the process of Example 1, We prepare a gaseous mixture ofacetylene, formaldehyde, and aniline and pass the resultant mixturethrough our reactor.

In place of the silica-alumina catalyst, we may use a large number ofother catalysts. In general, we find that among the catalysts useful incarrying out our reaction are those catalysts which have been founduseful in the preparation of 2-picoline and 4-picoline from acetylene(or acetaldehyde) and ammonia. Such catalysts include, in addition tothe silica-alumina catalyst of Example 1, alumina, silica,silica-magnesia, fullers earth, pumice, zinc chloride, zinc fluoride,cadmium chromate, cadmium fluoride, zinc phosphate, and the like.

Our invention does not reside in the discovery of a new catalyst. Whatwe have discovered is that the interaction of acetaldehyde, oracetylene, formaldehyde, and aniline yields quinoline of high purity andin commercially acceptable yields.

In Example 1 the molecular equivalents of the reactants areapproximately as follows: aniline, one mol; acetaldehyde, 0.77 mol;formaldehyde, 0.77 mol. We need not, however, use the specific molalratios of Example l. The proportions of the reactants may vary widely.In general, we prefer to use an excess of aniline although that is notnecessary.

The temperature at which our reaction may be conducted may be variedwidely. In general, we prefer to have the reaction temperatures aboveabout 400 C. and below about 550 C. It has been our experience that attemperatures below about 400 C., too large a proportion of the reactantspass through without reacting.

.At temperatures above about 550 C. we find our catalyst becomesinactivated rapidly and we obtain too many side reactions.

We claim as our invention:

1. The process of preparing quinoline which comprises mixing the vaporsof acetaldehyde, formaldehyde, and aniline, passing the resultantmixture through a reactor containing a silica-alumina catalystmaintained at a temperature between about 450 C. to about 500 C. andrecovering quinoline from the reaction product.

2. The process of preparing quinoline which comprises mixing the vaporsof acetaldehyde, formaldehyde, and aniline, passing the resultantmixture through a reactor containing an alumina catalyst maintained at atemperature between about 450 C. to about 500 C. and recoveringquinoline from the reaction product.

3. The process of preparing quinoline which comprises mixing the vaporsof acetaldehyde, formaldehyde, and aniline, passing the resultantmixture through a reactor containing a zinc fluoride catalyst maintainedat a temperature between about 450 C. to about 500 C. and recoveringquinoline from the reaction product.

References Cited in the file of this patent Elderfield: HeterocyclicCompounds, vol. IV, pp. 10 and 11, John Wiley, New York, N.Y., 1952.

1. THE PROCESS OF PREPARING QUINOLINE WHICH COMPRISES MIXING THE VAPORSOF ACETALDEHYDE, FORMALDEHYDE, AND ANILINE, PASSING THE RESULTANTMIXTURE THROUGH A REACTOR CONTAINING A SILICA-ALUMINA CATALYSTMAINTAINED AT A TEMPERATURE BETWEEN ABOUT 450* C. TO ABOUT 500* C. ANDRECOVERING QUINOLINE FROM THE REACTION PRODUCT.